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Aviation History
1960
1960 - 1306.PDF
216 FLIGHT, 12 August 1960 Among the open-class aircraft at the championships were (from the top) the American RHJ-6, West German Phonix and Swiss Elfe M SAILPLANES AT BITTZWEILER' ' ILLUSTRATED WITH "FLIGHT" PHOTOGRAPHS THE most interesting machines seen among the crop ofsailplanes at this year's World Gliding Championships atButzweiler Airfield, Cologne, were reviewed last month by Frank Irving, MEng, Die, AFRAes, in a talk at the Kronfeld Club,London. The main facts and comments presented on this occa- sion by Mr Irving, who is chairman of the British Gliding Associa-tion's technical committee, have formed the basis for the following type-by-type notes, which begin with the open-class aircraft.RHJ-6 (USA). Designed and built by Richard Johnson with no concessions to "styling," this aircraft was designed as a two-seater, but was flown with a solo cockpit at Butzweiler. Unlike the RJ-5 (wooden fuselage, metal wings) the RHJ-6 has a con-ventional all-wood structure—and a pretty solid structure at that, with ribs and frames cut from gaboon ply. No less than 601b oflead ballast was needed in the nose'to get the e.g. right. The rudder appeared to be too small, and probably was. An Eppler wing section is used, designed to keep the boundarylayer laminar as far back as possible and then to give low skin- friction under the turbulent boundary layer by operating close toseparation. This is not necessarily a good philosophy, since viscous losses in the boundary layer will somehow appear as drag—presumably form drag. But wind-tunnel tests showed slightly lower drag and wider bucket than a corresponding NACA sec-tion. During the championships Johnson suspected some pre- mature separation at low speeds, and attached a full-span line oftriangular cardboard vortex generators (results not known). A tee-tail is obviously useful for crop clearance on landing.The RHJ-6 tail is very heavily built, but it is not clear how much of the weight is due to asymmetric stressing cases. The slightdihedral obviously complicates the elevator linkage. Phonix (W. Germany). The tee-tail and Eppler wing-sectionare the only features which this aircraft has in common with the RHJ-6. Elegant in shape, the German machine looks as if it weredesigned by someone more accustomed to model gliders, since little regard seems to have been paid to such items as adequatecontrols. Its span is only 16 metres—extremely small for an open-class aircraft. The structure employs a glass-fibre/balsa/glass-fibre sandwich, with glass said to be only 0.1mm thick and hence easily bruised. The fuselage bottom was frequently bruisedin field landings during the championships, due to excessive deflection of the wheel, which pivots backwards for springingand still further back to retract. The wing finish is superb. Tests by Gus Raspet showed slightturbulent separation at high CL, but this did not seem to worry Haase as much as it did Johnson. According to Haase, theailerons were pathetically weak; hence the anti-servo tab on the rudder "to get round corners somehow." The tab is intendedprimarily to increase rudder effectiveness, not to increase hinge moment. The cut-out in the elevator to clear the rudder looks untidy,and not really necessary if the rudder shape were only slightly altered. Airbrakes consist of flaps slightly forward of the trailingedge of the wing lowered to 90° to act as brakes. This was not very effective near the ground andj as it presumably increasesCt as well as Co, it is not a good idea in general. The cockpit and canopy of the Phonix were very neat. No special instrumentswere fitted. Meteor 60 (Jugoslavia). This machine still looks very exoticbut less startling than the Polish newcomers. It is all-metal, 20 metres in span, very complicated and very expensive. Theaircraft is basically the same as the earlier Meteor 57, but with a cleaned-up centre-section/fuselage junction, involving thewidening of canopy at rear and fuselage shoulder. The Meteor has a very slender fuselage, but the attitude of the pilot is not extreme.The aircraft has been tested both with and without the wingtip "shapes"; according to Boris Cijan a better low-speed performancewas obtained with shapes fitted. Zefir 2 (Poland). This and the standard-class Foka were thetwo most interesting aircraft at the championships, and their most impressive feature was their extreme slimness. The Zefir employsa straightforward wooden structure in a very slender fuselage, attained by (a) a fairly flat seating attitude for the pilot—but notas extreme as one might imagine—plus (b) the elimination of control-runs under the seat. The pilot's posterior is only an inchor two from the bottom of the fuselage. This is achieved by unscrambling stick movements at the baseof the stick to work a push-pull rod for elevator and torque tube for ailerons, running along the fuselage sides under convenient Most of the open-class lime- light was focussed on the Polish Zefir 2 sailplanes, one of which is seen in the lower left photograph. Detail points of interest include the semi- reclining pilot position (below right), and the wingtip- mounted thermal detectors (right) which were fitted on several occasions
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